The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Kaarina Sarmaja-korjonen - One of the best experts on this subject based on the ideXlab platform.
-
Quantitative palaeotemperature estimates based on fossil chydorid Ephippia: calibration and validation of a novel method for northern lakes
Journal of Quaternary Science, 2015Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Seija Kultti, Kaarina Sarmaja-korjonenAbstract:To fully utilize palaeolimnological archives for tracking past environmental changes, methodological advances are necessary. We present a novel method to quantitatively reconstruct past summer air temperatures based on fossil chydorid (Cladocera: Chydoridae) Ephippia assemblages. We examined a 76-lake training set from Finland for chydorid Ephippia distribution to develop a transfer function for summer air temperatures. Subsequently, we tested its usability in downcore reconstructions by inferring Holocene temperatures from Lake Arapisto in southern Finland. Significant climate-related variation was found in the distribution and abundance of chydorid Ephippia in the training set. A transfer function for palaeotemperature reconstructions was developed using the partial least squares technique, which showed favourable performance statistics, enabling the test use of the model in a downcore reconstruction. The Ephippia assemblages were responding to the Holocene climate development in the Lake Arapisto core. The ephippium-inferred temperatures correlated closely with the previously available independent palaeoclimate data from Lake Arapisto and from an adjacent lake, although the early Holocene samples had poor modern analogues in the training set. The use of fossil chydorid Ephippia in palaeoclimatological reconstructions is a promising tool and it can contribute as a valuable addition for multiproxy assessments of past climate changes.
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence ( r ~ −0.8, P
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence (r ~ −0.8, P < 0.001) with several climate factors, especially that of mean July air temperature. We used this relationship to create a model for reconstructing past mean July air temperatures. A linear regression of the log10 transformed TCE as a single independent variable explained 76% (SE ± 0.76°C) of the variance of the observed mean July air temperatures. Accordingly, we propose that this novel tool may be highly suitable for reconstructing paleotemperatures in cold-temperate environments.
-
Multiproxy evidence for the ‘Little Ice Age’ from Lake Hampträsk, Southern Finland
Journal of Paleolimnology, 2008Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Kaarina Sarmaja-korjonenAbstract:We studied a short sediment core from Lake Hampträsk, southern Finland, for evidence of the ‘Little Ice Age’ (LIA) in aquatic invertebrate communities. Subfossil chironomids, cladocerans, and chydorid Ephippia were investigated, together with detrended correspondence analyses (DCAs) and loss-on-ignition (LOI). Our results show two cooler periods. The first cooling, indicated by increased numbers of chydorid Ephippia and cold-water chironomid taxa, occurred ca. 1400 AD and the second, more drastic cooling, during the seventeenth century, when cold-water chironomids began to increase. Our data suggest that the cooling culminated around 1700 AD, when cold-stenothermic chironomids and chydorid Ephippia attained maximal values and the LOI and diversity of invertebrates decreased to minimal values. After the LIA, the aquatic fauna appeared to respond to rising trophic state caused by enhanced land use in the catchment.
-
Chydorid Ephippia as Indicators of Past Environmental Changes – A New Method
Hydrobiologia, 2004Co-Authors: Kaarina Sarmaja-korjonenAbstract:I present a new method, ephippium analysis, to investigate past environmental changes which may have affected chydorid Cladocera (Anomopoda, Chydoridae). I studied chydorid Ephippia from sediments of two small lakes (Kaksoislammi and Rutikka) in southern Finland. The relative adundance of chydorid Ephippia periodically increased during the Holocene. Ephippia were abundant during the late Pleistocene/early Holocene transition, reflecting the severe climate (short open-water season) that existed prior to the onset of rapid postglacial warming. Both lakes experienced an environmental change in the late Holocene. In Kaksoislammi there was a dramatic change in predator–prey relationships following a decline in pH. All chydorids responded with increased gamogenesis. Prehistoric anthropogenic activities caused a rise in the trophic state in Rutikka and probably caused changes in the predator/food web. One chydorid, Alona affinis, reacted first with increased gamogenesis and then almost disappeared. These first results of ephippium analysis indicate that the method has a great potential in detecting periods of environmental change during the Holocene.
Tomi P. Luoto - One of the best experts on this subject based on the ideXlab platform.
-
Quantitative palaeotemperature estimates based on fossil chydorid Ephippia: calibration and validation of a novel method for northern lakes
Journal of Quaternary Science, 2015Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Seija Kultti, Kaarina Sarmaja-korjonenAbstract:To fully utilize palaeolimnological archives for tracking past environmental changes, methodological advances are necessary. We present a novel method to quantitatively reconstruct past summer air temperatures based on fossil chydorid (Cladocera: Chydoridae) Ephippia assemblages. We examined a 76-lake training set from Finland for chydorid Ephippia distribution to develop a transfer function for summer air temperatures. Subsequently, we tested its usability in downcore reconstructions by inferring Holocene temperatures from Lake Arapisto in southern Finland. Significant climate-related variation was found in the distribution and abundance of chydorid Ephippia in the training set. A transfer function for palaeotemperature reconstructions was developed using the partial least squares technique, which showed favourable performance statistics, enabling the test use of the model in a downcore reconstruction. The Ephippia assemblages were responding to the Holocene climate development in the Lake Arapisto core. The ephippium-inferred temperatures correlated closely with the previously available independent palaeoclimate data from Lake Arapisto and from an adjacent lake, although the early Holocene samples had poor modern analogues in the training set. The use of fossil chydorid Ephippia in palaeoclimatological reconstructions is a promising tool and it can contribute as a valuable addition for multiproxy assessments of past climate changes.
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence ( r ~ −0.8, P
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence (r ~ −0.8, P < 0.001) with several climate factors, especially that of mean July air temperature. We used this relationship to create a model for reconstructing past mean July air temperatures. A linear regression of the log10 transformed TCE as a single independent variable explained 76% (SE ± 0.76°C) of the variance of the observed mean July air temperatures. Accordingly, we propose that this novel tool may be highly suitable for reconstructing paleotemperatures in cold-temperate environments.
-
Multiproxy evidence for the ‘Little Ice Age’ from Lake Hampträsk, Southern Finland
Journal of Paleolimnology, 2008Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Kaarina Sarmaja-korjonenAbstract:We studied a short sediment core from Lake Hampträsk, southern Finland, for evidence of the ‘Little Ice Age’ (LIA) in aquatic invertebrate communities. Subfossil chironomids, cladocerans, and chydorid Ephippia were investigated, together with detrended correspondence analyses (DCAs) and loss-on-ignition (LOI). Our results show two cooler periods. The first cooling, indicated by increased numbers of chydorid Ephippia and cold-water chironomid taxa, occurred ca. 1400 AD and the second, more drastic cooling, during the seventeenth century, when cold-water chironomids began to increase. Our data suggest that the cooling culminated around 1700 AD, when cold-stenothermic chironomids and chydorid Ephippia attained maximal values and the LOI and diversity of invertebrates decreased to minimal values. After the LIA, the aquatic fauna appeared to respond to rising trophic state caused by enhanced land use in the catchment.
Liisa Nevalainen - One of the best experts on this subject based on the ideXlab platform.
-
Quantitative palaeotemperature estimates based on fossil chydorid Ephippia: calibration and validation of a novel method for northern lakes
Journal of Quaternary Science, 2015Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Seija Kultti, Kaarina Sarmaja-korjonenAbstract:To fully utilize palaeolimnological archives for tracking past environmental changes, methodological advances are necessary. We present a novel method to quantitatively reconstruct past summer air temperatures based on fossil chydorid (Cladocera: Chydoridae) Ephippia assemblages. We examined a 76-lake training set from Finland for chydorid Ephippia distribution to develop a transfer function for summer air temperatures. Subsequently, we tested its usability in downcore reconstructions by inferring Holocene temperatures from Lake Arapisto in southern Finland. Significant climate-related variation was found in the distribution and abundance of chydorid Ephippia in the training set. A transfer function for palaeotemperature reconstructions was developed using the partial least squares technique, which showed favourable performance statistics, enabling the test use of the model in a downcore reconstruction. The Ephippia assemblages were responding to the Holocene climate development in the Lake Arapisto core. The ephippium-inferred temperatures correlated closely with the previously available independent palaeoclimate data from Lake Arapisto and from an adjacent lake, although the early Holocene samples had poor modern analogues in the training set. The use of fossil chydorid Ephippia in palaeoclimatological reconstructions is a promising tool and it can contribute as a valuable addition for multiproxy assessments of past climate changes.
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence ( r ~ −0.8, P
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence (r ~ −0.8, P < 0.001) with several climate factors, especially that of mean July air temperature. We used this relationship to create a model for reconstructing past mean July air temperatures. A linear regression of the log10 transformed TCE as a single independent variable explained 76% (SE ± 0.76°C) of the variance of the observed mean July air temperatures. Accordingly, we propose that this novel tool may be highly suitable for reconstructing paleotemperatures in cold-temperate environments.
-
Multiproxy evidence for the ‘Little Ice Age’ from Lake Hampträsk, Southern Finland
Journal of Paleolimnology, 2008Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Kaarina Sarmaja-korjonenAbstract:We studied a short sediment core from Lake Hampträsk, southern Finland, for evidence of the ‘Little Ice Age’ (LIA) in aquatic invertebrate communities. Subfossil chironomids, cladocerans, and chydorid Ephippia were investigated, together with detrended correspondence analyses (DCAs) and loss-on-ignition (LOI). Our results show two cooler periods. The first cooling, indicated by increased numbers of chydorid Ephippia and cold-water chironomid taxa, occurred ca. 1400 AD and the second, more drastic cooling, during the seventeenth century, when cold-water chironomids began to increase. Our data suggest that the cooling culminated around 1700 AD, when cold-stenothermic chironomids and chydorid Ephippia attained maximal values and the LOI and diversity of invertebrates decreased to minimal values. After the LIA, the aquatic fauna appeared to respond to rising trophic state caused by enhanced land use in the catchment.
Seija Kultti - One of the best experts on this subject based on the ideXlab platform.
-
Quantitative palaeotemperature estimates based on fossil chydorid Ephippia: calibration and validation of a novel method for northern lakes
Journal of Quaternary Science, 2015Co-Authors: Tomi P. Luoto, Liisa Nevalainen, Seija Kultti, Kaarina Sarmaja-korjonenAbstract:To fully utilize palaeolimnological archives for tracking past environmental changes, methodological advances are necessary. We present a novel method to quantitatively reconstruct past summer air temperatures based on fossil chydorid (Cladocera: Chydoridae) Ephippia assemblages. We examined a 76-lake training set from Finland for chydorid Ephippia distribution to develop a transfer function for summer air temperatures. Subsequently, we tested its usability in downcore reconstructions by inferring Holocene temperatures from Lake Arapisto in southern Finland. Significant climate-related variation was found in the distribution and abundance of chydorid Ephippia in the training set. A transfer function for palaeotemperature reconstructions was developed using the partial least squares technique, which showed favourable performance statistics, enabling the test use of the model in a downcore reconstruction. The Ephippia assemblages were responding to the Holocene climate development in the Lake Arapisto core. The ephippium-inferred temperatures correlated closely with the previously available independent palaeoclimate data from Lake Arapisto and from an adjacent lake, although the early Holocene samples had poor modern analogues in the training set. The use of fossil chydorid Ephippia in palaeoclimatological reconstructions is a promising tool and it can contribute as a valuable addition for multiproxy assessments of past climate changes.
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence ( r ~ −0.8, P
-
Subfossil chydorid (Cladocera, Chydoridae) Ephippia as paleoenvironmental proxies: evidence from boreal and subarctic lakes in Finland
Hydrobiologia, 2011Co-Authors: Seija Kultti, Liisa Nevalainen, Tomi P. Luoto, Kaarina Sarmaja-korjonenAbstract:Chydorids (Cladocera, Chydoridae) have two reproductive strategies: asexual reproduction that prevails during favorable environmental conditions and sexual reproduction that is induced by environmental stimuli associated with seasonal or aperiodic environmental stresses. These modes of reproduction can be recognized in the subfossil sedimentary records as parthenogenetic shells of females (asexual reproduction) and by Ephippia (sexual reproduction). We studied the interrelations between subfossil chydorid Ephippia and environmental variables by analyzing surface sediment samples obtained from 76 Finnish lakes across a latitudinal gradient (60–70°N). The results showed that the total chydorid Ephippia (TCE) increases along the climate gradient from ~2 to 3% in the south to ~25% in the north and suggested a significant dependence (r ~ −0.8, P < 0.001) with several climate factors, especially that of mean July air temperature. We used this relationship to create a model for reconstructing past mean July air temperatures. A linear regression of the log10 transformed TCE as a single independent variable explained 76% (SE ± 0.76°C) of the variance of the observed mean July air temperatures. Accordingly, we propose that this novel tool may be highly suitable for reconstructing paleotemperatures in cold-temperate environments.
Hazel Monica Matiasperalta - One of the best experts on this subject based on the ideXlab platform.
-
effect of food density on male appearance and Ephippia production in a tropical cladoceran moina micrura kurz 1874
Aquaculture, 2013Co-Authors: Osman M Azuraidi, Fatimah Md Yusoff, Mariana Nor Shamsudin, Rahim A Raha, Victor R Alekseev, Hazel Monica MatiasperaltaAbstract:A study was conducted to investigate the effects of different food concentrations consisting of Nannochloropsis oculata (4 × 102, 4 × 104, 4 × 106 cells ml− 1 and control) on male and Ephippia production in a tropical cladoceran, Moina micrura. The highest number of males (186.7 ± 13.4 males l− 1) was produced in cultures fed with 4 × 102 cells ml− 1 of N. oculata (FC 3) when the population density reached > 1600 individuals l− 1. Similarly, the highest total mean number of Ephippia (160.0 ± 0.0 Ephippia l− 1) was achieved in M. micrura culture supplied with 4 × 102 cells ml− 1 of N. oculata (FC 3). The second highest Ephippia density was found in M. micrura cultures fed with 4 × 104 cells ml− 1 of N. oculata (FC 2) which produced a mean total of 93.3 ± 13.4 Ephippia l− 1 in a population density of > 3000 individuals l− 1. However, with a population density of > 4000 individuals l− 1, but fed with the highest food concentration of 4 × 106 cells ml− 1 N. oculata (FC 1), no Ephippia was produced although males were present in the culture. This study illustrates that Ephippia were produced in high density cultures with the presence of males and insufficient food supply. Crowding could trigger the production of males, but was not an adequate stress factor for inducing the formation of Ephippia. Similarly, food limitation alone did not induce the production of males and Ephippia without crowding.